TeacherOfMedicine: Glucose (dextrose)

Glucose 5% is used to provide water intravenously in patients unable to take enough orally.
Glucose 10%, 20% and 50% are used to treat hypoglycaemia when this is severe or cannot be treated orally. Glucagon is an alternative.
Glucose 10%, 20% and 50% are used with insulin to treat hyperkalaemia. Calcium gluconate may also be given in this setting.
Glucose 5% is used for reconstitution and dilution of drugs intended for administration by injection or infusion. Sodium chloride 0.9% and sterile water are alternatives.

Glucose (C₆H₁₂O₆) is a monosaccharide that is the principal source of energy for cellular metabolism.
It exists in several isomeric configurations, of which d-glucose (dextrose) is the one used in nature.

When given in a 5% solution, glucose has a negligible calorific content. The glucose makes the solution initially isotonic and prevents it from inducing osmolysis.
As only about 7% of the administered volume remains in the intravascular space (since the intravascular compartment is about 7% of total body water), glucose is not a suitable fluid for expanding circulating volume.
In hyperkalaemia, insulin (usually Actrapid®) is given to stimulate Na⁺/K⁺-ATPase and shift potassium into cells. Glucose is given simply to prevent hypoglycaemia.

Glucose 50% is highly irritant to veins and may cause local pain, phlebitis and thrombosis. For this reason, its use is now discouraged, unless it can be given via a central line. Glucose 20% is also irritant.
Hyperglycaemia will occur if glucose administration exceeds its utilisation (which is most likely in patients with diabetes mellitus).

In patients at risk of thiamine deficiency, giving IV glucose can cause Wernicke’s encephalopathy.
In renal failure, close monitoring of fluid balance is essential to avoid overload.
Administering a significant volume of hypotonic fluid may precipitate hyponatraemic encephalopathy in patients with hyponatraemia or high susceptiblity to its effects (e.g. children).

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